The present invention is directed to valve structures of the type disclosed in U.S. Pat. No. 3,260,496, and which valve principally utilizes a unilateral sealing means. A bidirectional cryogenic valve structure is disclosed in U.S. Pat. No. 3,650,508 granted on Mar. 21, 1972. These patented structures are particularly adapted for controlling the flow of cryogenic fluids, including liquid and gaseous hydrogen, nitrogen, oxygen, and methane, as well as many other ambient temperature bipropellants and corrosive fluids. The sealing means utilized in such cryogenic valves provided virtually leakproof action. The sealing means principally utilized in these valve structures are constructed entirely of resilient plastic materials, such as Teflon or the like, and are subject to being destroyed by fire conditions at the valve thereby rendering the valve inoperative or subject to leaks. It has been found that sealing means constructed entirely of plastic material require frequent replacement when the valve is used in throttling type service. It has also been found that when such prior art valve sealing structures are utilized for handling liquefied gas, LNG, that the fluid contains sand, dirt, or similar foreign particles that may become crushed between the valve disc sealing means, thereby scratching or damaging the sealing surfaces, both the resilient seal and the disc sealing surface, whereby the sealing qualities of the valve are deteriorated. The problem is particularly troublesome where metallic sealing means are used. The handling of liquefied natural gas, LNG, has been found to be fire prone and LNG valves now must meet the specification of having a fire safe seat in the form of metallic sealing means. Various types of sealing means for these cryogenic and special fluid handling means are available and are presently sold as providing a fire safe seal, including metallic seals. I have no knowledge, however, of a valve structure for an LNG application that is directed to the problem of preventing sand, dirt or similar foreign particles from affecting the sealing qualities of such cryogenic valves.